スクリーン印刷法による高温超伝導体厚膜の作製

概要

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High-T_c superconducting Y-Ba-Cu oxide thick films were produced on various substrates (quartz, sapphire, MgO and YSZ) by the screen-printing method. The reactions between the substrates and the screen-printed superconductor under several firing conditions were studied using scanning electron microscopy, EDX analysis and powder X-ray diffraction analysis. For the YSZ substrates, BaZrO_3 was generated at the interface between the superconductor and the substrate upon firing at 990℃ in an oxygen atmosphere. As Ba ions diffused into the substrate, parts of printed ceramic changed to Y_2BaCuO_5. Thick-film densification and interfacial reaction occurred in the same temperature range. When the firing time at 990℃ was made as short as possible, the greatest fraction of the screen-printed ceramic remained fully-dense YBa_2Cu_3O_<7-δ>. A superconducting thick film on YSZ with T_<c,onset>=89 K, T_<c,end>=87 K and J_c(77K) =30 A/cm^2 was obtained. The rate of the thermal expansion of YBa_2Cu_3O_<7-δ> was also measured. The thermal expansion coefficient of YBa_2Cu_3O_<7-δ> was 18.7X10^<-6> K^<-1> and had a maximum at around 600℃, near the orthorhombic- tetragonal phase transition temperature in air.
社団法人日本セラミックス協会の論文
1988-04-01